Dual-arm articulated hinge for the front bonnet of a motor vehicle

ABSTRACT

A double-armed hinge for use in a motor vehicle, includes a first bar for fastening to a front bonnet of said motor vehicle, a second bar for fastening to a body of said motor vehicle, a first arm, a second arm, and a thrust piece. At least one of said first arm and said second arm is constructed in two parts and includes a first strut and a second strut. The thrust piece thrust piece is applied to one of said first strut and said second strut. The thrust piece includes a head configured to grip behind the first or second strut. The first and second struts are pivotably connected to each other by a connecting joint and rigidly braced to each other by a connection device. The connecting device yields under a given load so that, under a sudden load that exceeds the given load, the connection device breaks and the first and second bars come closer to each other substantially without resistance.

[0001] The invention relates to a double-armed hinge for the front hoodof a motor vehicle with a first and a second arm between a bar connectedto the front hood and a bar connected to the body.

[0002] Such hinges come to use in manifold modes. A very schematicillustration can be seen from DE 197 12 961. The bottom ends of the armsare connected to the body by a bar and the upper ends to the front hoodby a bar in respective joints. Since the arms are differently long andthe joint axes at the top and at the bottom show different distances,the front hood is displaced when swinging up at the same time upward andforward. With other words: the pivot axis of the front hood passesthrough a path which is defined by the hinge geometry.

[0003] For the construction of a hinge for a front hood, care hasfurther to be taken that the front hood is designed to yield to acertain amount, such that a pedestrian who is seized by a vehicle andimpacts with his body and head onto the front hood is injured to a lesspossible amount. The restrictions following therefrom which have to beconsidered during the construction are checked using defined head-impactsimulations. During these experiments, the deceleration of a simulationhead is measured. From the chronological course of the deceleration, theso called HIC value can be determined, the definition thereof beingavailable from the technical literature, and which should exceed 1,000to fulfill certain obligations.

[0004] Very critical are head impacts on the front hood in the region ofthe hinges, since at this place a connection of the front hood to thebody is provided which cannot be designed as yielding that the presetHIC value can fall short of. In the already cited laid-open publication,there is proposed to provide the bar at the body as a bracket beingpivotable upwards. The bracket is, in case of an impending collisionwith a pedestrian, positioned by a prestressed spring in a wedge-typemanner. On the one hand, the path along which the impacting head canreduce its kinetic energy is extended. On the other hand, the springrate defines quiet exactly the resistance which causes the headdeceleration. But it is problematic that it is extremely difficult toensure that the front hood is lifted in the correct moment. Further, adeceleration corresponding to a spring characteristic is not necessarilyoptimal in view of obtaining as low an HIC value as possible.

[0005] The invention is based on the problem to construct a double-armedhinge in such a manner that in case of a head impact on a front hood inthe region of the hinges the injuries are as reduced as possible, i.e.that the HIC value in a simulation measures, if possible, under 1,000.

[0006] The solution of this problem is a hinge according to the preambleof claim 1 with the further features that at least one arm isconstructed in two parts and consists of two struts which are pivotablyconnected to each other by means of a connecting joint and rigidlyattached to each other by means of a connection which yields under agiven load so that, when the connection yields as a result of a suddenload, the bars come close to each other substantially withoutresistance.

[0007] This arrangement has the advantage that it is independent from aspecial activation of the protection mechanism, e.g. a prestressedspring. The protection mechanism is moreover inherently present and doesnot need an external triggering burdened by accident sensitiveness andincertitude.

[0008] The cause of the deceleration achieved in this manner induces anHIC value under 1,000. Namely and first of all a relatively largedeceleration is given before the connection of the struts cedes, butthis is limited to a short time and therefor supportable for theimpacting head. Afterwards, a phase of reduced deceleration is providedwhen, after ceding of the connection, the bars come close to each otherwithout resistance. Not until the bars come together, a distinctdeceleration happens which in view of its consequences for the headinjury is no more significant, since the kinetic energy of the head hasbeen reduced largely during the first impact of the head. The two-stepdeceleration generated in this manner delivers good HIC values.

[0009] The yielding can be achieved in different manners. E.g., aweakening in the material of the arms could be considered such that thearms bend through in response to a load. Systems have been proven asparticular suitable where the yielding is achieved through a breaking ofthe connection. Therethrough, a non-ambiguous defined threshold load isachieved.

[0010] To realize such a site of fracture, the struts are designed insuch a manner that they lie against each other, in overlapping planarrelationship, and in the overlap region comprise the connecting jointand have a shear pin passing through them. Such an assembly is easily toarrange and fulfils the foreseen function in non-ambiguous manner.

[0011] In order to transfer the impact forces in a defined manner ontothe struts, a thrust piece is provided on the bar for mounting the fronthood. Said thrust piece can be applied to one of the struts of thetwo-part arm and induces the impact forces acting upon the front hood ona defined point of the strut in a distance of the jointed connectionwith the other strut such that the shear pin which has a differentdistance to the joint is loaded upon at a predetermined ratio withrespect to the impact force. The arrangement of the thrust piece occursin such a manner that it is moved away from the two-part arm duringswinging up of the front hood.

[0012] In a more general manner, the thrust piece can be applieddirectly to the two-part arm when the front hood is closed, wherethroughthe thrust piece has, at the same time, the function to define theclosed position of the hinge.

[0013] This function can also be performed by another abutment. In thiscase, the thrust piece will have a certain distance to the strut suchthat it hits in case of a head impact with a momentum onto the struthaving as consequence that the shearing process is jerkily achieved andonly necessitates very short time such that the transfer to the phasewith reduced deceleration is even more clearly defined.

[0014] A particular simple embodiment of the thrust piece is achievedwhen it is designed as a bolt which protrudes laterally from the bar forattachment of the front hood.

[0015] In order to avoid slipping of the thrust piece from the strutduring the transmission of the impact force, it is provided that thethrust piece comprises a head which penetrates into a gap between thetwo struts and in this manner grips behind the loaded strut.

[0016] In order to realise the gap, the strut to which the thrust piececan be applied comprises an end portion which is offset with respect tothe other strut.

[0017] To illustrate the invention, an embodiment of the invention willsubsequently be explained in more detail with respect to the threedrawings.

[0018]FIG. 1 shows a side view of a hinge according to the invention inthe normal position.

[0019]FIG. 2 shows a cut along line II-II of FIG. 1.

[0020]FIG. 3 shows the hinge according to FIG. 1 after accomplishing ahead impact simulation test.

[0021] First, reference is made to FIG. 1 and 2. FIG. 1 shows in a sideview a double-armed hinge 1. Said hinge consists of an upper bar 2 and alower bar 3. The upper bar is bolted together, welded together ordesigned in one part with a front hood not shown. The lower bar isbolted together with a body strut not shown. The two bars 2, 3 arepivotably connected with each other with a long arm 4 and a short arm 5.For this purpose, each arm 4, 5 is pivotably beared as well to the upperas to the lower bar in joints 6, 7, 8, 9. The upper bar 2 consists of avertical portion 10 for receiving the joints 8, 9 and a horizontalportion 11 to which the front hood is fastened. The lower bar 3comprises also a vertical portion 12 having two regions 13, 14 beingoffset with respect to each other in a right angle to the image plane,wherein the one region 13 to which the long arm 4 is pivotably beared ina joint 6 lies in the same plane as the vertical portion 10 of the upperbar 2, and the other region 14 receiving the joint 7 for the short arm 5is offset with respect thereto. On the last cited region 14 is a fixedclamp 15 for fastening the lower bar 3 to a body strut.

[0022] According to the illustration the long arm 4 is provided behindthe vertical portions 10 while the short arm 5 lies in front of it. Theshort arm 5 is embodied in two parts and consists of two struts 16, 17which are connected with each other by a connecting joint 18 in apivotable manner. This connecting joint 18 is provided approximately athalf distance between the two joints 7, 9 at the bars 2, 3. The lowerstrut 16 which is pivotably connected with the lower bar 3 is extendedover the connecting joint 18 and lies in this region against the upperstrut 17 in a planar relationship, wherein in this region the two struts16, 17 are traversed by a shear pin 19.

[0023] The lower strut 16 is extended over the shear pin 19 and isoffset in steps from the upper strut 17 which is particularly good to beseen in FIG. 2. Therethrough, a gap 20 is designed between the twostruts 16, 17.

[0024] A head 21 of a thrust piece 22 designed as a bolt penetrates intothis gap 20, serving as thrust piece for transmitting of forces onto theshort arm 5. The thrust piece 22 is firmly attached to the verticalportion 10 of the upper bar 2 and protrudes normally.

[0025] The shear pin 19 connects the two struts 16, 17 of the short arm5 in rigid manner such that it operates like a single-piece arm and thedouble-armed hinge 1 works as designed for. Even facing static forces ina normal range, the forces which are urged onto the short arm 5 by thethrust piece 22 are not that high that this rigid connection would brakeup.

[0026] In case of a head impact the exercised forces exceed the shearlimit at which the shear pin 19 shears such that the connection isreleased. When namely a hit force according to arrow 23 is exercised onthe upper bar 2, it is transferred via the thrust piece 22 onto theshort arm 5 and from there according to the effective lever armsaccording to arrow 24 onto shear pin 19.

[0027] In the shown embodiment, the thrust piece 22 is applied directlyagainst the lower strut 16 and the short arm 5. A shorter distance canbe provided here also to let the force transmission be achieved with acertain impetus. The head 21 gripping behind lower strut 16 preventsthat the thrust piece 22 slides in doing so from the strut 16 whichwould avoid a force transmission.

[0028] When within a sudden load a threshold load is reached where theshear pin 19 shears, the rigid connection between the two struts 16, 17is suspended and these can rotate with respect to each other aroundconnecting joint 18. Therethrough it is possible that the upper bar 2sags downward, as shown in FIG. 3. In doing so, the hinge opposes noresistance against the movement such that the head deceleration resultsonly from a deformation of the hood or of a deformation of thesupporting elements outside the hinge, respectively. But these aredesigned in a manner that the deceleration is only reduced. Only whenthe hinge is completely collapsed, as shown in FIG. 3, and the upperstrut 17 lies onto the lower strut 16, a rigid connection to the body isproduced again such that again high decelerations occur. It resultsaccordingly a two-step deceleration course in total, namely a first stepuntil the shearing of the shear pin 19 and second step after collapsingof the hinge, where in total a reduced HIC value can be expected.

List of Reference Signs

[0029]1 double-armed hinge

[0030]2 upper bar

[0031]3 lower bar

[0032]4 long arm

[0033]5 short arm

[0034]6 joint

[0035]7 joint

[0036]8 joint

[0037]9 joint

[0038]10 vertical portion

[0039]11 horizontal portion

[0040]12 vertical portion

[0041]13 region

[0042]14 region

[0043]15 clamp

[0044]16 lower strut

[0045]17 upper strut

[0046]18 connecting joint

[0047]19 shear pin

[0048]20 gap

[0049]21 head

[0050]22 thrust piece

[0051]23 arrow

[0052]24 arrow

1-8: (canceled). 9: A double-armed hinge for use in a motor vehicle,comprising: a first bar for fastening to a front bonnet of said motorvehicle; a second bar for fastening to a body of said motor vehicle; afirst arm and a second arm wherein at least one of said first arm andsaid second arm is constructed in two parts and comprises a first strutand a second strut; and a thrust piece applied to one of said firststrut and said second strut; wherein said thrust piece includes a headconfigured to grip behind said one of said first strut and said secondstrut, and wherein said first strut and said second strut are pivotablyconnected to each other by a connecting joint and rigidly braced to eachother by a connection device which yields under a given load so that,under a sudden load that exceeds the given load, the connection devicebreaks and the first and second bars come closer to each othersubstantially without resistance. 10: The double-armed hinge accordingto claim 9, wherein said head penetrates into a gap between said firststrut and said second strut. 11: The double-armed hinge according toclaim 10, wherein, to form said gap, said one of said first strut andsaid second strut comprises an end portion which is offset with respectthe other of said first strut and said second strut. 12: Thedouble-armed hinge according to claim 9, wherein in a closed position ofsaid front bonnet, a space is provided between said one of said firststrut and said second strut and said thrust piece. 13: The double-armedhinge according to claim 9, wherein said first strut and said secondstrut lie against each other in overlapping planar relationship andwherein said connection comprises a shear pin passing through said firststrut and said second strut in an overlap region. 14: The double-armedhinge according to claim 9, wherein said thrust piece is a bolt, andwherein said bolt protrudes laterally from said first bar. 15: Thedouble-armed hinge according to claim 9, wherein said first arm and saidsecond arm each comprise a first joint for bearing in said first bar anda second joint for bearing in said second bar.